1. Field of the Invention
The present invention relates to vehicular airbag cushions. More specifically, the present invention relates to modular airbag cushions which can be connected to other airbag cushions in order to facilitate providing airbag protection over a relatively long area such as the side of a minivan or sport utility vehicle.
2. Technical Background
Inflatable safety restraint devices, or airbags, are now required by law to be installed in most new vehicles. Airbags are typically installed in the steering wheel and in the dashboard on the passenger side of a car. In the event of an accident, an accelerometer within the vehicle measures the abnormal deceleration and triggers the ignition of an explosive charge. Expanding gases from the charge fill the airbags, which immediately inflate in front of the driver and passenger to protect them from impact against the windshield.
Side impact airbags, also known as inflatable curtains, have been developed in response to the need for similar protection from impacts in a lateral direction, or against the side of the vehicle. These side impact airbags are typically located within the roof rails of the vehicle. When they are inflated they descend down from the roof and form a barrier between the occupants and the side of the vehicle.
Despite their enormous lifesaving potential, the effectiveness of side impact airbags has been somewhat limited by the speed with which inflation gases are able to fill the cushion. Side impact cushions are often designed to unfold or unroll downward to inflate beside a person to keep the person from hitting the door or window during lateral impact. Since a vehicle occupant may be leaning forward, reclined in the seat, or at any position between, such cushions are often made somewhat long to ensure that the occupant hits the cushion. The cushions must also be designed such that the seatbelts and seat backs of the vehicle do not catch the inflatable airbag curtain. The curtains may be provided with dead zones which do not inflate, but allow the curtain to inflate around seatbelts, seat backs, and other obstacles in the vehicle. The dead zones may also connect the various inflatable protecting zones of the airbag curtain creating a single tension line along a side of a vehicle when the curtain is inflated.
Cushions for inflatable curtains are often inflated by an inflator positioned either fore or aft of the cushion. Consequently, unlike many front impact airbags, a long gas flow path exists between the inflator and the outermost extent of the cushion. The length of the gas flow path is problematic for a number of reasons. The cushions are unable to inflate rapidly enough to provide optimal protection. Since most airbag systems are unable to detect a collision until impact has begun to occur, the airbag must move from an uninflated, stowed configuration, to a fully inflated configuration, within a small fraction of a second. The long flow path increases the time required by the inflation gases to traverse the cushion. Thus, the cushion may not obtain a fully inflated state before the vehicle occupant strikes the cushion.
Some inflatable curtains are designed to protect only the passengers of the front seats. Other inflatable curtains may be designed to protect both the occupants of the front seats and the seats directly behind the front seats. For example, in a vehicle with three seating areas, such as a minivan or sport-utility vehicle, these side impact cushions only have protection zones for the front and middle seats. The occupants of the rear seat are not protected by the airbag cushion.
Recently, inflatable curtains have been developed to protect passenger in all three rows of passenger seating in minivans and sport utility vehicles. In an airbag cushion designed to protect passengers in three seating areas, there may be a problem with uniform inflation of the cushion. Generally, long airbag cushions are inflated by a single inflator. Using a single inflator for all protection zones costs less than using multiple inflators for the cushion. The use of one inflator also reduces the risk of airbag malfunction. However, because the airbags use one inflator, there may be unequal pressure buildup in the protection zones. The pressure buildup can cause the cushion to inflate in a non-uniform manner preventing the protection of the vehicle occupants.
The long curtains are also expensive to manufacture and install in minivans or sport utility vehicles. Before a curtain is installed in a vehicle, it is generally folded or rolled and then inserted into a package known as a sock. Specially manufactured large folding machines are necessary to fold the long curtains. The use of special equipment adds to the cost of the final airbag system. Additionally, packaging these long curtains into the vehicle from the A-pillar to the D-pillar is also proving difficult for the car manufacturer. The production of very long cushions can be troublesome and require special training and equipment which again adds to the cost of the airbag system.
Generally, the airbag cushions have zones which do not inflate, but serve to connect the inflation zones. These dead zones add weight to the airbag cushion. Moreover, because the dead zones use the same amount of fabric and other materials as the inflating protection zones, the cost of this unused fabric and materials add to the overall cost of the airbag system.
Today's vehicles come with a variety of accessory systems. These accessory systems include rear heating and cooling, private audio systems for the passengers, and theatre systems just to name a few. These systems require significant wiring and duct work. Generally, the wiring and duct work are concealed within the roof or floor of the vehicle. However, the space available in the roof and floor of the vehicle is very limited. Wiring and duct work contained in the floor of the vehicle may be damaged by the feet of vehicle occupants, thus the roof is the preferred location. Inflatable curtains and their wiring and duct work must compete with the accessory systems for space within the roof of the vehicle. The problem of limited space within the roof of the vehicle is compounded by the dead zones or connecting zones which are typically present in inflatable curtains. These dead zones require as much space as an inflating zone, but do not inflate to protect vehicle occupants.
The specific seating arrangement of a vehicle depends on the body type and manufacturer of the vehicle. That is the seating arrangement of a minivan of a manufacturer will differ from the seating arrangement of a sport utility vehicle of the same manufacturer. Additionally, the seating arrangement of a minivan or sport utility vehicle of a second manufacturer will be different than the seating arrangement in the minivan and sport utility vehicle of the first manufacturer. Thus, the seats of the vehicle may be spaced closer or farther from each other depending on the particular vehicle type and manufacturer. Because of the non-uniformity of seating arrangements in vehicles, airbag curtains must be designed and manufactured for each specific vehicle make and model. The cost of such cushions is increased because the airbag curtains cannot be mass designed and produced for many different types of vehicles.
Accordingly, a need exists for a side impact airbag cushion configured to protect occupants of all seats of a vehicle. In particular, a need exists for an apparatus that can provide side impact protection for the occupants of the front, middle, and rear seats of a vehicle. It would be an additional improvement if the airbag cushion allowed for a more uniform inflation of the cushion. A need further exists for such an apparatus and method that minimizes the expense of manufacture and installation of the cushion. Furthermore, a need exists for an inflatable curtain airbag that minimizes the space required for installation. It would be an additional improvement to provide a cushion that allows a cushion or cushions to be designed for and installed in a number of types of vehicles with different manufactures. It would be a further advancement to provide an inflatable airbag curtain that minimizes dead zones.